1. Field of the Invention
The present invention generally relates to cooling mechanisms for cooling electric driving parts of injection molding machines and cooling methods for the same, and more particularly, to a cooling mechanism for cooling an electric driving part of a hybrid type injection molding machine having an actuating part actuated by being supplied an actuating fluid, and a cooling method for the same.
2. Description of the Related Art
In an injection molding machine, resin heated and melted in a heating cylinder is injected into a cavity of a mold apparatus under high pressure so that the cavity is filled with the molten resin. The molten resin is then cooled and solidified so as to obtain a molded article.
Such an injection molding machine includes an injection apparatus, a mold clamping apparatus and the mold apparatus. The mold apparatus is provided with a stationary side mold unit and a movable side mold unit. The movable side mold unit is advanced and retracted by the mold clamping apparatus, so as to perform mold closing, mold clamping and mold opening.
The injection apparatus includes a heating cylinder and a screw. The screw is disposed inside the heating cylinder so that the screw can be rotated about an axis and can be advanced and retracted. The screw is advanced so that the resin is injected from the injection nozzle provided at a head end of the heating cylinder, and thereby the resin fills the cavity space of the mold apparatus.
Furthermore, the injection apparatus includes an injection apparatus main part supported on a frame of the injection molding machine and a moving apparatus for plasticizing. By operating the moving apparatus for plasticizing, the injection apparatus main part is advanced and retracted, and a nozzle opening part formed at a head end of the injection nozzle can come in contact with and separate from a stationary platen of the stationary side mold unit. The resin is injected from the injection nozzle in a state where the nozzle opening comes in contact with the stationary platen.
Meanwhile, there is a hybrid type injection molding machine in the field of injection molding machines. The hybrid injection molding machine includes an electric driving part such as an electric motor and an actuating part. Oil is supplied as an actuating fluid to the actuating part so that the actuating part is actuated by hydraulic pressure.
In such a hybrid type injection molding machine, a hydraulic actuating part is actuated for injection. An electrically powered machine such as a motor is driven for mold clamping, metering and moving for plasticizing (other than for injection) as an electric driving part, so that mold closing, mold clamping, mold opening, metering, retraction so-called suck back, nozzle touch, ejecting a molded article, and others are performed.
In a case where the electrically powered machine(motor) is used as the driving part, normally, a fan provided with the motor is operated for air-cooling the motor forcibly so as to correspond to heat generation based on motor driving (forced air cooling method).
Furthermore, not only the above mentioned forced air cooling method but also a cooling fluid passing method is applied for cooling the electrically powered machine as a driving part of the injection molding machine. In the cooling fluid passing method, a jacket is provided at an external circumference of the electric driving part. A cooling fluid path is formed by a groove of the jacket, so that cooling fluid such as water or oil is passed through the cooling fluid path, thereby cooling the electric driving part.
However, in the forced air cooling method, the electric driving part is cooled only by the fan. Hence, it may be difficult to sufficiently dissipate the heat generated by driving the electric driving part. Therefore, the rated output of the heat of the electric driving part is required to be small.
Furthermore, in the cooling fluid passing method, separate equipment having a large size is necessary. Hence, the injection molding machine is required to have a large size and manufacturing cost is increased. In addition, in a case where water is used as the cooling fluid, for example, corrosion may occur inside of the cooling fluid path due to poor water quality, and condensation may occur when water temperature is lower than air temperature. The above mentioned occurrences of corrosion and condensation may cause a problem such as an electrical short of the motor.